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authorShreshtha Kumar Sahu <shreshthakumar.sahu@stericsson.com>2011-06-09 22:56:32 +0200
committerGreg Kroah-Hartman <gregkh@suse.de>2011-07-08 15:09:23 -0700
commitdef90f4239f094f3846c108c1c41a4cd55c33e8e (patch)
tree4afa3043999cca62d501764456b194db33fea224 /drivers
parentf086ced17191fa0c5712539d2b680eae3dc972a1 (diff)
amba pl011: workaround for uart registers lockup
This workaround aims to break the deadlock situation which raises during continuous transfer of data for long duration over uart with hardware flow control. It is observed that CTS interrupt cannot be cleared in uart interrupt register (ICR). Hence further transfer over uart gets blocked. It is seen that during such deadlock condition ICR don't get cleared even on multiple write. This leads pass_counter to decrease and finally reach zero. This can be taken as trigger point to run this UART_BT_WA. Workaround backups the register configuration, does soft reset of UART using BIT-0 of PRCC_K_SOFTRST_SET/CLEAR registers and restores the registers. This patch also provides support for uart init and exit function calls if present. Signed-off-by: Shreshtha Kumar Sahu <shreshthakumar.sahu@stericsson.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/tty/serial/amba-pl011.c123
1 files changed, 122 insertions, 1 deletions
diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 8dc0541feecc..f5f6831b0a64 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -50,6 +50,7 @@
#include <linux/dmaengine.h>
#include <linux/dma-mapping.h>
#include <linux/scatterlist.h>
+#include <linux/delay.h>
#include <asm/io.h>
#include <asm/sizes.h>
@@ -65,6 +66,30 @@
#define UART_DR_ERROR (UART011_DR_OE|UART011_DR_BE|UART011_DR_PE|UART011_DR_FE)
#define UART_DUMMY_DR_RX (1 << 16)
+
+#define UART_WA_SAVE_NR 14
+
+static void pl011_lockup_wa(unsigned long data);
+static const u32 uart_wa_reg[UART_WA_SAVE_NR] = {
+ ST_UART011_DMAWM,
+ ST_UART011_TIMEOUT,
+ ST_UART011_LCRH_RX,
+ UART011_IBRD,
+ UART011_FBRD,
+ ST_UART011_LCRH_TX,
+ UART011_IFLS,
+ ST_UART011_XFCR,
+ ST_UART011_XON1,
+ ST_UART011_XON2,
+ ST_UART011_XOFF1,
+ ST_UART011_XOFF2,
+ UART011_CR,
+ UART011_IMSC
+};
+
+static u32 uart_wa_regdata[UART_WA_SAVE_NR];
+static DECLARE_TASKLET(pl011_lockup_tlet, pl011_lockup_wa, 0);
+
/* There is by now at least one vendor with differing details, so handle it */
struct vendor_data {
unsigned int ifls;
@@ -72,6 +97,7 @@ struct vendor_data {
unsigned int lcrh_tx;
unsigned int lcrh_rx;
bool oversampling;
+ bool interrupt_may_hang; /* vendor-specific */
bool dma_threshold;
};
@@ -90,9 +116,12 @@ static struct vendor_data vendor_st = {
.lcrh_tx = ST_UART011_LCRH_TX,
.lcrh_rx = ST_UART011_LCRH_RX,
.oversampling = true,
+ .interrupt_may_hang = true,
.dma_threshold = true,
};
+static struct uart_amba_port *amba_ports[UART_NR];
+
/* Deals with DMA transactions */
struct pl011_sgbuf {
@@ -132,6 +161,7 @@ struct uart_amba_port {
unsigned int lcrh_rx; /* vendor-specific */
bool autorts;
char type[12];
+ bool interrupt_may_hang; /* vendor-specific */
#ifdef CONFIG_DMA_ENGINE
/* DMA stuff */
bool using_tx_dma;
@@ -1008,6 +1038,68 @@ static inline bool pl011_dma_rx_running(struct uart_amba_port *uap)
#endif
+/*
+ * pl011_lockup_wa
+ * This workaround aims to break the deadlock situation
+ * when after long transfer over uart in hardware flow
+ * control, uart interrupt registers cannot be cleared.
+ * Hence uart transfer gets blocked.
+ *
+ * It is seen that during such deadlock condition ICR
+ * don't get cleared even on multiple write. This leads
+ * pass_counter to decrease and finally reach zero. This
+ * can be taken as trigger point to run this UART_BT_WA.
+ *
+ */
+static void pl011_lockup_wa(unsigned long data)
+{
+ struct uart_amba_port *uap = amba_ports[0];
+ void __iomem *base = uap->port.membase;
+ struct circ_buf *xmit = &uap->port.state->xmit;
+ struct tty_struct *tty = uap->port.state->port.tty;
+ int buf_empty_retries = 200;
+ int loop;
+
+ /* Stop HCI layer from submitting data for tx */
+ tty->hw_stopped = 1;
+ while (!uart_circ_empty(xmit)) {
+ if (buf_empty_retries-- == 0)
+ break;
+ udelay(100);
+ }
+
+ /* Backup registers */
+ for (loop = 0; loop < UART_WA_SAVE_NR; loop++)
+ uart_wa_regdata[loop] = readl(base + uart_wa_reg[loop]);
+
+ /* Disable UART so that FIFO data is flushed out */
+ writew(0x00, uap->port.membase + UART011_CR);
+
+ /* Soft reset UART module */
+ if (uap->port.dev->platform_data) {
+ struct amba_pl011_data *plat;
+
+ plat = uap->port.dev->platform_data;
+ if (plat->reset)
+ plat->reset();
+ }
+
+ /* Restore registers */
+ for (loop = 0; loop < UART_WA_SAVE_NR; loop++)
+ writew(uart_wa_regdata[loop] ,
+ uap->port.membase + uart_wa_reg[loop]);
+
+ /* Initialise the old status of the modem signals */
+ uap->old_status = readw(uap->port.membase + UART01x_FR) &
+ UART01x_FR_MODEM_ANY;
+
+ if (readl(base + UART011_MIS) & 0x2)
+ printk(KERN_EMERG "UART_BT_WA: ***FAILED***\n");
+
+ /* Start Tx/Rx */
+ tty->hw_stopped = 0;
+}
+
static void pl011_stop_tx(struct uart_port *port)
{
struct uart_amba_port *uap = (struct uart_amba_port *)port;
@@ -1158,8 +1250,11 @@ static irqreturn_t pl011_int(int irq, void *dev_id)
if (status & UART011_TXIS)
pl011_tx_chars(uap);
- if (pass_counter-- == 0)
+ if (pass_counter-- == 0) {
+ if (uap->interrupt_may_hang)
+ tasklet_schedule(&pl011_lockup_tlet);
break;
+ }
status = readw(uap->port.membase + UART011_MIS);
} while (status != 0);
@@ -1339,6 +1434,14 @@ static int pl011_startup(struct uart_port *port)
writew(uap->im, uap->port.membase + UART011_IMSC);
spin_unlock_irq(&uap->port.lock);
+ if (uap->port.dev->platform_data) {
+ struct amba_pl011_data *plat;
+
+ plat = uap->port.dev->platform_data;
+ if (plat->init)
+ plat->init();
+ }
+
return 0;
clk_dis:
@@ -1394,6 +1497,15 @@ static void pl011_shutdown(struct uart_port *port)
* Shut down the clock producer
*/
clk_disable(uap->clk);
+
+ if (uap->port.dev->platform_data) {
+ struct amba_pl011_data *plat;
+
+ plat = uap->port.dev->platform_data;
+ if (plat->exit)
+ plat->exit();
+ }
+
}
static void
@@ -1700,6 +1812,14 @@ static int __init pl011_console_setup(struct console *co, char *options)
if (!uap)
return -ENODEV;
+ if (uap->port.dev->platform_data) {
+ struct amba_pl011_data *plat;
+
+ plat = uap->port.dev->platform_data;
+ if (plat->init)
+ plat->init();
+ }
+
uap->port.uartclk = clk_get_rate(uap->clk);
if (options)
@@ -1774,6 +1894,7 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id)
uap->lcrh_rx = vendor->lcrh_rx;
uap->lcrh_tx = vendor->lcrh_tx;
uap->fifosize = vendor->fifosize;
+ uap->interrupt_may_hang = vendor->interrupt_may_hang;
uap->port.dev = &dev->dev;
uap->port.mapbase = dev->res.start;
uap->port.membase = base;